Problem to be Solved and Significance: Exposure to Ultraviolet radiation (UVR) is a risk factor for the development of skin cancer, and health care agencies recommend that sunscreens be used as a preventative measure. A major limitation of commercial sunscreens is the need to continually reapply to gain full benefit. This is because sunscreens contain UV filters that lack affinity with skin and are easily removed by normal wear. The development of durable filters with improved retention on skin has the potential to mitigate UV- mediated toxicities and remains a significant priority. Product and Long-Term Goal: Nanometics (d.b.a. PHD Biosciences [PHD]) is developing novel titanium dioxide and zinc oxide UV filters that contain a coating that interacts with skin proteins to improve topical retention time. The novel UV filters are synthesized from inexpensive starting materials and will be sold globally as ingredients for sunscreens and other topical products. It is anticipated that these UV filters will alleviate the need for constant product reapplication. Technological Innovation: The surface of commercial titanium dioxide and zinc oxide UV filters is covalently modified to contain a coating that interacts with skin proteins to improve topical retention time. The coating is designed to form a stable interaction at skin pH, and can easily be removed by washing with soap. Specific Aim #1. To determine the SPF and water-resistance properties of the HPGA-Filters on healthy volunteers. The hypotheses to be tested are: the new filters will exhibit no significant differences in the Sun Protection Factor (SPF) on healthy volunteers compared to commercial controls; are more resistant to removal with water from healthy volunteers than commercial controls; and are readily removed by washing with soap. Commercial Opportunity: The global market for UV filters is estimated to exceed $650 million by 2019. Phase II SBIR studies will include additional studies to confirm the safety on a larger number of volunteers; examine the performance against leading commercial sunscreens; and optimize the chemistry, manufacturing, and control (CMC) processes to produce the filters in multi-kilogram quantities. The technology is covered by a pending patent that protects the PHD commercial and development interests.